Habitat Flashcards
(65 cards)
The every day life definition (Webster’s New Collegiate Dictionary)
“The upper layer of earth which can be dug or plowed and in which plants grow”
This is the engineering definition of soil (Spangler and Handy, 1982)
“All the fragmented mineral material at or near the surface of the earth, the moon, or other planetary body, plus the air, water, organic matter, and other substances which may be included therein”
This geological definition of soil introduces the idea of alteration in place as a distinction between soil and sediment. (Nature 391, 12, 1998)
“Material altered in place at the surface of a planetary body by physical, chemical or biological means.”
Soil science definition (Buckman and Brady, 1970, The Nature and Properties of Soils)
Emphasizes the strong two-way interactions between biota and the soil habitat (Coleman & Crossley, 1996, Soil Ecology)
“A natural body, synthesized in profile form from a variable mixture of broken and weathered minerals and decaying organic matter, which covers the earth in a thin layer and which supplies, when containing the proper amounts of air and water, mechanical support and, in part, sustenance for plants”
“…with its living organisms…”
The pedosphere
the envelope of Earth where soils occur and soil forming factors are active
Where does the pedosphere develop?
where there is a close interaction between the atmosphere (soil air), biosphere(litter and organisms), hydrosphere (soil water), and lithosphere (soil and minerals)
Soil formation
stage 1
- Bedrock is weathered into parental material (unconsolidated rock fragments)
- Parent material can stay in one place or be transported by gravity, water, wind, glaciers
soil formation
stage 2
initial horizons are formed by additions, removals, mixing and transformations
(mixing can be done by worms)
soil formation
stage 3
mature soil is formed by further differentiation of soil horizons
Soils are dynamic bodies (function of time t) that respond to variety of soil forming factors (Jenny 1941):
S = (climate, parent material, biota, topography, vegetation)t + human (t2)
what does it mean that soil responds to a variety of factors?
that there is a considerable diversity within soils
Variability and complexity of soils
- large variation of soil types across globe
- depth of where bedrock starts increases from arctic to tropical climate (equator)
soil taxonomy
- 12 orders
- inceptisoil makes up 17%, most common soil type
A pedon
minimum of 3 dimensions of a soil that are necessary to describe it
In which layer are the most microbes?
…
Horizontal soil variability (small scale)
dependnet on pH, Carbon
What serious problem is there with the measurement of temporal patterns in soil ecology?
What examples can you think of, on what time scales?
???
“typical soil” percentage of dry weight
93% mineral
7% organic matter
organic portion of soil dry weight
85% dead
10% plant roots
5% Edaphon
soil biota percentage dry weight
40% Bacteria & Actinomycetes 40% Algae & Fungi 12% Earthworms 5% other macrofauna 3% mesofauna
sand
2mm-50µm
11-227 cm^3/g
silt
50µm-2µm
454 cm^3/g
clay
<2µm
8,000,000 cm^3/g
(can be a size fraction, a texture class name or/and a class of minerals)
loam
perfect mixture of sand silt and clay
